1. Field of the Invention
The present invention relates to a guided-wave optical circuit and method for adjusting a characteristic of the guided-wave optical circuit disposed on a substrate, in which the coupling ratio of a directional coupler or an optical path length of a guided-wave optical circuit is adjusted by changing their refractive indices by using a thermal hysteresis phenomenon of a material constituting the guided-wave optical circuit.
2. Description of the Prior Art
Single-mode optical waveguides fabricated on a plane substrate, in particular, silica-based single mode waveguides which are fabricated on a silicon substrate or silica grass substrate are expected as a promising means for implementing practical guided-wave optical devices (guided-wave optical circuits) which are superior in matching with optical fibers. This is because diameters of the silica-based single mode waveguides can be made about 5-10 .mu.m, which match common sizes of sectional areas of the cores of single-mode optical fibers (for example, see N. Takato, et al. "Silica-Based Single-Mode Waveguides on Silicon and Their Application to Guided-Wave Optical Interferometers, Journal of Lightwave Technology", Vol. 6, No. 6, June 1988, pp. 1003-1010, or Masao Kawachi, "Silica-based optical waveguides and their application to integrated optical devices", Optics 18, (1989), pp. 681-686.